有关电流控制放大器CCA的说法正确的是（）。

A.主要是一个PI调节器

B.比例环节实现快速调节

C.积分环节稳态时保持触发角为定值

D.需具备快速性和稳定性

______we were worried about was ________they could manage to control the pollution.

A．That how

B．That whether

C．What that

D．What whether